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| United States Patent |
5,151,464
|
|
Yang
|
September 29, 1992
|
Miscible polyblends of acid-and anhydride-containing copolymers
Abstract
Miscible polyblends of acid-containing and anhydride-containing styrenic
copolymers are described. In a preferred embodiment, the polyblend
contains a styrene/maleic anhydride copolymer and a styrene/methacrylic
acid copolymer.
| Inventors:
|
Yang; Lau S. (Wilmington, DE)
|
| Assignee:
|
Arco Chemical Technology, L.P. (Wilmington, DE)
|
| Appl. No.:
|
752753 |
| Filed:
|
August 30, 1991 |
| Current U.S. Class: |
524/449; 524/451; 524/504; 524/517; 525/74; 525/207 |
| Intern'l Class: |
C08L 035/06; C08L 025/08 |
| Field of Search: |
525/207,74
524/441
|
References Cited
U.S. Patent Documents
| 4657975 | Apr., 1987 | Kodama et al. | 525/207.
|
| 5047480 | Sep., 1991 | Leitz et al. | 525/207.
|
| Foreign Patent Documents |
| 3332326 | Mar., 1985 | DE | 525/74.
|
| 3332327 | Mar., 1985 | DE | 525/207.
|
| 60-120736 | Jun., 1985 | JP.
| |
Primary Examiner: Seccuro, Jr.; Carman J.
Attorney, Agent or Firm: Harper; Stephen D.
Claims
I claim:
1. A miscible polyblend comprised of
(a) an acid-containing copolymer comprised of, in polymerized form, from 5
to 20 weight percent of an .alpha.,.beta.-unsaturated carboxylic acid
selected from methacrylic acid and acrylic acid and from 80 to 95 weight
percent of a first vinyl aromatic monomer; and
(b) an anhydride-containing copolymer comprised of, in polymerized form,
from 5 to 20 weight percent of an .alpha.,.beta.-unsaturated dicarboxylic
acid anhydride and from 80 to 95 weight percent of a second vinyl aromatic
monomer;
with the proviso that the amount of .alpha.,.beta.-unsaturated carboxylic
acid in the acid-containing copolymer is not more than 75 percent greater
than the amount of .alpha.,.beta.-unsaturated dicarboxylic acid anhydride
in the anhydride-containing copolymer and characterized by the absence of
a styrene butadiene block copolymer.
2. The miscible polyblend of claim 1 wherein the .alpha.,.beta.-unsaturated
carboxylic acid is methacrylic acid.
3. The miscible polyblend of claim 1 wherein the first and second vinyl
aromatic monomers are each styrene.
4. The miscible polyblend of claim 1 wherein the .alpha.,.beta.-unsaturated
dicarboxylic acid anhydride is maleic anhydride.
5. The miscible polyblend of claim 1 wherein the amount of the
.alpha.,.beta.-unsaturated carboxylic acid in the acid-containing
copolymer is no more than 50 percent greater than the amount of
.alpha.,.beta.-unsaturated discarboxylic acid anhydride in the
anhydride-containing copolymer.
6. The miscible polyblend of claim 1 wherein the acid-containing copolymer
is comprised of from 8 to 17 weight percent .alpha.,.beta.-unsaturated
carboxylic acid and from 83 to 92 weight percent of the first vinyl
aromatic monomer.
7. The miscible polyblend of claim 1 wherein the anhydride-containing
copolymer is comprised of from 6 to 16 weight percent
.alpha.,.beta.-unsaturated dicarboxylic acid anhydride and from 84 to 94
weight percent of the second vinyl aromatic monomer.
8. The miscible polyblend of claim 1 additionally comprising at least one
additive selected from the group consisting of stabilizers, colorants,
fillers, processing acids, plasticizers, impact modifiers other than
styrene butadiene block copolymers, flame retardants, and blowing agents.
9. A molded article produced by molding the composition of claim 1.
10. A miscible polyblend comprised of
(a) from 20 to 80 weight percent of an acid-containing copolymer comprised
of, in polymerized form, from 8 to 17 weight percent methacrylic acid and
from 83 to 92 weight percent styrene; and
(b) 20 to 80 weight percent of an anhydride-containing copolymer comprised
of, in polymerized form, from 6 to 16 weight percent maleic anhydride and
from 84 to 94 weight percent styrene;
with the proviso that the amount of methacrylic acid in the acid-containing
copolymer is not more than 50 percent greater than the amount of maleic
anhydride in the anhydride-containing copolymer and characterized by the
absence of a styrene butadiene block copolymer compatibilizer.
11. The miscible polyblend of claim 10 wherein the acid-containing
copolymer has a weight average molecular weight of from about 100,000 to
500,000.
12. The miscible polyblend of claim 10 wherein the anhydride-containing
copolymer has a weight average molecular weight of from about 100,000 to
500,000.
13. The miscible polyblend of claim 10 additionally comprising at least one
additive selected from the group consisting of stabilizers, colorants,
fillers, processing acids, plasticizers, impact modifiers other than
styrene butadiene block copolymers, flame retardants, and blowing agents.
14. The miscible polyblend of claim 10 additionally comprising a
reinforcing filler selected from the group consisting of glass flakes,
glass fibers, carbon fibers, graphite fibers, plastic fibers, metals,
ceramics, silicates, titanium dioxide, mica, and talc.
15. The miscible polyblend of claim 10 additionally comprising from 5 to 40
parts by weight glass fibers per 100 parts by weight of the miscible
polyblend.
16. The miscible polyblend of claim 10 wherein the amount of
acid-containing copolymer is from 40 to 60 weight percent and the amount
of anhydride-containing copolymer is from 40 to 60 weight percent.
17. The miscible polyblend of claim 10 wherein the acid-containing
copolymer is rubber-modified, with the proviso that the rubber is not a
styrene butadiene block copolymer.
18. The miscible polyblend of claim 10 wherein the anhydride-containing
copolymer is rubber-modified, with the proviso that the rubber is not a
styrene butadiene block copolymer.
19. The miscible polyblend of claim 17 wherein the rubber-modified
acid-containing copolymer is prepared by polymerizing the methacrylic acid
and styrene in the presence of a diene rubber other than a styrene
butadiene block copolymer under free radical polymerization conditions.
20. The miscible polyblend of claim 18 wherein the rubber-modified
anhydride-containing copolymer is prepared by polymerizing the maleic
anhydride and styrene in the presence of a diene rubber other than a
styrene butadiene block copolymer under free radical polymerization
conditions.
21. A molded article produced by molding the composition of claim 10.
Description
FIELD OF THE INVENTION
This invention pertains to miscible polyblends of acid-containing
copolymers and anhydride-containing copolymers useful for the production
of thermoplastic molded articles. In particular, the invention relates to
blends of styrene/methacrylic acid copolymers and styrene/maleic anhydride
copolymers.
BACKGROUND OF THE INVENTION
Copolymers of vinyl aromatic monomers and .alpha.,.beta.-unsaturated
dicarboxylic acid anhydrides have long been known in the art as useful,
relatively low cost engineering thermoplastics having superior heat
resistance as compared to styrene homopolymers. Styrene/maleic anhydride
copolymer resins are available commercially, for example, from ARCO
Chemical Company under the tradename "Dylark" and are widely used for the
production of molded articles such as automobile instrument panels and
other interior trim parts, appliance housings, furniture, and the like.
Such copolymers are now also gaining acceptance in packaging applications
such as microwave food containers.
Due to the hydrolytic instability of the .alpha.,.beta.-unsaturated
dicarboxylic acid anhydride monomer component, however, such copolymers
must generally be produced using bulk or non-aqueous solution
polymerization processes. These processes require specialized equipment
and are relatively costly due to the need to separate the final copolymer
product, which typically has a high viscosity in solution or in the melt
phase, from the unreacted monomer or organic solvent. Thus, if a
manufacturer wishes to expand production capacity for such resins, new
bulk or solution polymerization reactors and devolatilization facilities
must be constructed. It would be highly desirable if existing suspension
polymerization facilities, such as those commonly used to prepare styrene
homopolymer beads, could be employed for the production of
anhydride-containing copolymers, but this is not feasible owing to the
hydrolysis which readily occurs when the anhydride monomer is exposed to
water.
An alternative approach, in principle, would be to extend the
anhydride-containing copolymer by blending it with another polymeric
resin. However, it is well known in the polymer art that most polymers are
immiscible with one another. Typically, when an attempt is made to prepare
a uniform or homogeneous polyblend, the resulting mixture exhibits two or
more glass transition temperatures indicating two or more separate phases.
This inhomogeneity may adversely affect the physical and mechanical
properties of the resin mixture and typically results in an undesirable
opaque or hazy appearance in contrast to the transparency of the unblended
anhydride-containing copolymer. In the art, the incompatibility of
different polymers is the accepted rule and the discovery of fully
miscible polymeric blends is the exception to the rule.
SUMMARY OF THE INVENTION
I have now unexpectedly discovered that vinyl aromatic
monomer/.alpha.,.beta.-unsaturated dicarboxylic anhydride copolymers may
be blended with vinyl aromatic monomer/unsaturated carboxylic acid
copolymers to produce miscible polyblends by carefully balancing the
relative proportions of acid and anhydride in the individual components of
the blends. These miscible polyblends exhibit single glass transition
temperatures and have extraordinary clarity. Moreover, the physical and
mechanical properties of the anhydride-containing copolymer are not
compromised by blending with the acid-containing copolymer.
This finding of miscibility was surprising in view of Japanese Kokai
60-120,736, which teaches that styrene/methacrylic acid copolymers and
rubber-modified styrene/maleic anhydride copolymers are incompatible
(i.e., not miscible). A styrene butadiene block copolymer must be employed
in order to compatibilize these two types of polymers, according to the
publication. However, the prior art did not recognize the criticality of
balancing the relative proportions of acid and anhydride in the copolymers
to be blended. That is, in the specific binary blends attempted by the
publication, the anhydride content of the anhydride-containing copolymer
was 8 weight percent while the acid content of the acid-containing
copolymer was 15 weight percent. I have now found that the acid content
must be no more than 75% greater than the anhydride content in order to
achieve miscibility in the resulting polyblend.
This invention provides a miscible polyblend comprised of (a) an
acid-containing copolymer comprised of, in polymerized form, from 5 to 20
weight percent of an .alpha.,.beta.-unsaturated carboxylic acid selected
from methacrylic acid and acrylic acid and from 80 to 95 weight percent of
a first vinyl aromatic monomer and (b) an anhydride-containing copolymer
comprised of, in polymerized form, from 5 to 20 weight percent of an
.alpha.,.beta.-unsaturated dicarboxylic acid anhydride and from 80 to 95
weight percent of a second vinyl aromatic monomer. The amount (i.e.,
concentration) of .alpha.,.beta.-unsaturated carboxylic acid in the
acid-containing copolymer must not be more than 75 percent greater than
the amount of .alpha.,.beta.-unsaturated dicarboxylic acid anhydride in
the anhydride-containing copolymer
One particular advantage of the polyblends of this invention compared to
similar prior art mixtures is that no compatibilizer or interfacial
modifier is needed, owing to the complete miscibility of the acid- and
anhydride-containing copolymers. Thus, in a preferred embodiment, the
blends of this invention are characterized by the absence of a
compatibilizer such as a styrene butadiene block copolymer.
DETAILED DESCRIPTION OF THE INVENTION
The first necessary component of the miscible polyblend of this invention
is an acid-containing copolymer comprised of, in polymerized form, from 5
to 20 weight percent of an .alpha.,.beta.-unsaturated carboxylic acid and
from 80 to 95 weight percent of a vinyl aromatic monomer. The
.alpha.,.beta.-unsaturated carboxylic acid may be methacrylic acid,
acrylic acid, or a mixture thereof, but most preferably is methacrylic
acid. The amount of .alpha.,.beta.-unsaturated carboxylic acid
incorporated in the acid-containing copolymer is more preferably from 8 to
17 weight percent, with the amount of vinyl aromatic monomer being
correspondingly from 83 to 92 weight percent in this preferred embodiment.
The acid-containing copolymer most desirably has a random, linear
structure and a weight average molecular weight of from about 100,000 to
500,000.
For reasons of cost and availability, styrene is the preferred vinyl
aromatic monomer. However, other vinyl aromatic monomers may be used
either alone or in combination with each other or with styrene. For
example, substituted styrenes such as alkyl substituted styrenes (e.g.,
o-, m-, or p- methyl styrene, p-tert-butyl styrene, the various dimethyl
styrenes, alpha-methyl styrene, and the like), halogenated styrenes (e.g.,
chlorostyrenes, dichlorostyrenes, bromostyrenes, tribromostyrenes, vinyl
benzyl chloride), as well as styrenic monomers bearing other functional
groups such as acetoxystyrene will be suitable. Fused ring vinyl aromatic
monomers such as the vinyl naphthalenes, and alkyl and/or halo-substituted
vinyl naphthalenes may also be employed. Optionally, up to about 50 weight
percent of the vinyl aromatic monomer may be replaced by one or more
polymerizable unsaturated monomers such as olefins, aliphatic or aromatic
esters of unsaturated carboxylic acids (e.g., methyl methacrylate),
unsaturated ethers, unsaturated nitriles (e.g., acrylonitrile),
unsaturated carboxylic acids other than methacrylic acid or acrylic acid,
vinyl halides, vinyl esters, and the like.
Methods for making styrenic copolymers having the composition described
hereinabove are well-known in the art and are described, for example, in
U.S. Pat. Nos. 2,927,095, 3,839,308, 4,275,182, 3,035,033, 4,195,169,
4,631,307, 4,937,298, Japanese Kokai Nos. 61-252209 and 60-248708, and
European Pat. Nos. 381,432, 405,872, and 410,607. The teachings of these
publications are incorporated herein by reference in their entirety.
In one embodiment of this invention, the acid-containing copolymer is
rubber-modified (i.e., contains a rubber-like or elastomeric polymer). The
incorporation of the rubber makes the overall polymer blend significantly
tougher and less brittle (i.e., more ductile). Preferably, the
acid-containing copolymer is rubber-modified by copolymerization of the
vinyl aromatic monomer and unsaturated monocarboxylic acid in the presence
of the rubber. For this purpose, it is desirable that the rubber is a
diene rubber, that is, an elastomeric polymer wherein at least one
monomeric component is a diene. Such diene rubbers are well-known and, in
many instances, commercially available and include, for example,
styrene-butadiene-styrene (S-B-S) and styrene-isoprene-styrene (S-I-S)
block copolymers, styrene/butadiene and styrene/isoprene multiblock
copolymers (which may have a radial, linear, star, or tapered structure),
styrene/butadiene rubber (SBR), polybutadiene, polyisoprene,
ethylene-propylene-diene monomer (EPDM) rubbers,
styrene-butadiene-caprolactone block terpolymers, and the like and
partially hydrogenated derivatives thereof. The amount of the rubber is
not critical, but generally will be from about 5 to 65 parts by weight per
100 parts by weight of the acid-containing copolymer.
Commercially available acid-containing copolymers may also be used to
prepare the miscible polyblends of this invention. For example, the
styrene/methacrylic acid copolymer resins available from Dainippon Ink and
Chemical Inc. under the tradename "Ryulex" are suitable for use.
The other necessary component of the miscible polyblend of this invention
is an anhydride-containing copolymer comprised of, in polymerized form,
from 5 to 20 weight percent of an .alpha.,.beta.-unsaturated dicarboxylic
acid anhydride and from 80 to 95 weight percent of a vinyl aromatic
monomer. In a preferred embodiment, the amount of anhydride incorporated
in the anhydride-containing copolymer is from 6 to 16 weight; the amount
of vinyl aromatic monomer in this embodiment will thus be from 84 to 94
weight percent. The anhydride-containing copolymer most desirably has a
random, linear structure and a weight average molecular weight of from
about 100,000 to 500,000.
Although any suitable vinyl aromatic monomer may be employed in the
anhydride-containing copolymer, styrene is the preferred monomer because
of its low cost and availability. Examples of other vinyl aromatic
monomers which can be used include, but are not limited to, ar-methyl
styrene, ar-ethyl styrene, ar-tert-butyl styrene, ar-chloro styrene,
alpha-methyl styrene, divinyl benzene, vinyl benzyl chloride,and vinyl
naphthalene, as well as other alkyl- or halo-substituted styrenes.
Mixtures of vinyl aromatic monomers can be used. The vinyl aromatic
monomer in the anhydride-containing copolymer is most preferably the same
as the vinyl aromatic monomer in the acid-containing copolymer.
Unsaturated dicarboxylic acid anhydrides suitable for inclusion in the
anhydride-containing copolymer component include those organic compounds
which are polymerizable under free radical conditions and which have a
carbon-carbon double bond in conjugation with a carbon-oxygen double bond.
Exemplary unsaturated dicarboxylic acid anhydrides include itaconic
anhydride, citraconic anhydride, ethyl maleic anhydride, methyl itaconic
anhydride, chloromaleic anhydride, bromomaleic anhydride,
tetrahydrophthalic anhydride, and, most preferably, maleic anhydride. If
desired, mixtures of .alpha.,.beta.-unsaturated dicarboxylic acid
anhydrides can be used.
Optionally up to about 50 weight percent of the vinyl aromatic monomer in
the anhydride-containing copolymer may be replaced by one or more other
copolymerizable ethylenically unsaturated monomers. This optional
copolymerizable ethylenically unsaturated monomer may be selected from the
group consisting of unsaturated nitriles (e.g., acrylonitrile and
methacrylonitrile), unsaturated carboxylic acid esters (especially C.sub.1
-C.sub.4 alkyl esters such as methyl methacrylate and ethyl acrylate),
unsaturated dicarboxylic acid imides (e.g., maleimide, N-phenylmaleimide)
and mixtures thereof. Terpolymers of styrene, maleic anhydride, and
acrylonitrile or styrene, maleic anhydride, and methyl methacrylate are
particularly preferred.
In the most preferred embodiment of this invention, the
anhydride-containing copolymer is a copolymer of styrene and maleic
anhydride and has a melt flow rate (Condition L) of from about 0.1 to 10
g/10 min.
Rubber-modified anhydride-containing copolymers may also be employed. Such
copolymers preferably contain from about 1 to 35 (more preferably, from
about 5 to 25) weight percent of a grafted rubber. The grafted rubber is
preferably selected from the group consisting of conjugated diene rubbers
and ethylene-propylene-diene monomer rubbers.
Conjugated diene rubbers suitable for use as the grafted rubber preferably
contain at least about 50 weight percent of a conjugated diene and have
glass transition temperatures less than about 0.degree. C. (more
preferably, less than about -20.degree. C.). Such rubbers include
homopolymers, random copolymers, and block copolymers of conjugated
1,3-dienes such as 1,3-butadiene (a preferred diene), isoprene,
chloroprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and the like. The
conjugated diene rubber is preferably selected from the group consisting
of mono-vinyl aromatic monomer/conjugated diene block copolymers,
mono-vinyl aromatic monomer/conjugated diene random copolymers, conjugated
diene homopolymers, and mixtures thereof.
The conjugated diene rubber may contain one or more copolymerizable
ethylenically unsaturated comonomers. Most preferably, the comonomer is a
mono-vinyl aromatic monomer such as styrene, ar-methyl styrene, ar-ethyl
styrene, ar-tert-butyl styrene, ar-chlorostyrene, alpha-methyl styrene,
vinyl benzyl chloride, vinyl naphthalene, and the like and mixtures
thereof. Other copolymerizable ethylenically unsaturated monomers may be
employed, however, including unsaturated nitrile monomers such as
acrylonitrile and methacrylonitrile, alkyl acrylates such as methyl
methacrylate, methyl acrylate, butyl acrylate, or 2-ethylhexyl
methacrylate, acrylamides such as acrylamide, methacrylamide, or
butylacrylamide, unsaturated ketones such as vinyl methyl ketone or methyl
isopropenyl ketone, .alpha.-olefins such as ethylene or propylene, vinyl
esters such as vinyl acetate or vinyl stearate, vinyl heterocyclic
monomers such as vinyl pyridine, vinyl and vinylidene halides such as
vinyl chloride or vinylidene chloride, and the like and mixtures thereof.
In a preferred embodiment of this invention, the comonomer used in
combination with the 1,3-conjugated diene is the same as the vinyl
aromatic monomer component of the anhydride-containing copolymer.
Exemplary conjugated diene rubbers suitable for rubber modifying the
anhydride-containing copolymer include styrene/butadiene and
styrene/isoprene block copolymers. Such block copolymers may be linear,
radial, or branched in structure. Linear block copolymers may have an ABA,
AB(AB).sub.n A, (AB).sub.n, or similar structure wherein A represents a
block of the mono-vinyl aromatic monomer, B represents a block of the
conjugated diene and n is an integer of 1 to 10. Radial block copolymers
may have an (AB).sub.n X structure, wherein X is a multi-valent linking
agent. Block copolymers of these types are well-known. Details concerning
their preparation, structure, and properties may be found, for example, in
the following references: "Styrene-Diene Block Copolymers" Encyclopedia of
Polymer Science and Technology 1st Ed., Suppl., Wiley, pp 508-530(1971),
K. E. Snavely et al, Rubber World 169, 45(1973), and "Thermoplastic
Elastomers" Kirk Othmer Encyclopedia of Chemical Technology 3rd., Vol. 8,
Wiley-Interscience, pp 627-632(1981).
The following U.S. patents, incorporated herein by reference, further
describe such block copolymer conjugated diene rubbers: U.S. Pat. Nos.
3,937,760, 3,231,635, 3,265,765, 3,198,774, 3,078,254, 3,244,644,
3,280,084, 3,954,452, 3,766,301, 3,281,383, 4,640,968, 4,503,188,
4,485,210, 4,390,663, 4,271,661, and 4,346,193. Suitable block copolymers
are also presently available from commercial sources. Examples of
commercially available block copolymer rubbers include "STEREON 840A" (a
linear graded styrene/butadiene multi-block copolymer containing about 43%
styrene and having a number average molecular weight of about 60,000, sold
by Firestone Synthetic Rubber and Latex Co.), "STEREON 730A" (a
stereospecific tapered styrene/butadiene block copolymer containing a
total of 30% styrene with 21% styrene in block form and having a number
average molecular weight of 140,000, sold by Firestone Synthetic Rubber
and Latex Company), "KRATON D-1101" (a linear styrene/butadiene/styrene
triblock copolymer containing 31% styrene, sold by Shell Chemical),
"KRATON D-1107" (a linear styrene/isoprene/styrene triblock copolymer
containing 14% styrene, sold by Shell Chemical), and "KRATON D-1184" (a
branched styrene/butadiene multiblock copolymer containing 30% styrene,
sold by Shell Chemical).
Also suitable for use as conjugated diene rubbers in the rubber-modified
anhydride-containing copolymer component of this invention are random
copolymers of mono-vinyl aromatic monomers and conjugated dienes. A
particularly preferred conjugated diene rubber of this type is
styrene/butadiene rubber (SBR). Homopolymers of conjugated dienes such as
polybutadiene and polyisoprene may also be employed as the rubber. All
such rubbers are well-known in the art and are described, for example, in
"Butadiene Polymers" Encyclopedia of Polymer Science and Engineering 2nd
Ed., Wiley-Interscience, Vol. 2, pp. 537-590(1988), the teachings of which
are incorporated by reference herein in their entirety.
The grafted rubber may alternatively be an ethylene propylene diene monomer
(EPDM) rubber. Such materials are well-known in the art and are random
copolymers of ethylene, at least one C.sub.3 -C.sub.6 .alpha.-olefin
(preferably propylene), and at least one nonconjugated diene. The
nonconjugated diene may be a linear aliphatic diene of at least six carbon
atoms which has either two terminal double bonds or one terminal double
bond and one internal double bond. Alternatively, the nonconjugated diene
may be a cyclic diene where one or both of the double bonds are part of a
carboxcyclic ring. The structure of the EPDM rubber may be altered as
desired, particularly with respect to branching, by the selection of
particular nonconjugated dienes as is well known in the art. Particularly
preferred non-conjugated dienes include 1,4-hexadiene, dicyclopentadiene,
vinyl norbornene, norbornadiene, and 5-ethylidene-2-norbornene.
Preferably, the EPDM rubber contains from about 40 to 90 mole percent
ethylene and 0.1 to 7.5 mole percent nonconjugated diene, with the
remainder being propylene. Additional information regarding EPDM rubbers
may be found in "Ethylene-Propylene Elastomers" Encyclopedia of Polymer
Science and Engineering 2nd Ed., Wiley-Interscience, Vol. 6, p.
522-564(1986), the teachings of which are incorporated herein by reference
in their entirety.
The anhydride-containing copolymers useful in the compositions of this
invention may be prepared by any of the several methods available for
their synthesis. For example, the copolymers may be obtained by solution
copolymerization directly from the respective monomers by the incremental
addition of the more reactive monomer as taught by U.S. Pat. No. 2,971,939
or by a continuous recycle polymerization process described in U.S. Pat.
Nos. 2,769,804 and 2,989,517. Rubber-modified anhydride-containing
copolymers may be prepared by incorporation of the rubber into the monomer
mixture prior to polymerization using, for example, the methods of U.S.
Pat Nos. 4,097,551 and 3,919,354. The teachings of all these patents are
incorporated herein by reference. Suitable commercially available
anhydride-containing copolymers include the "Dylark" styrene/maleic
anhydride resins produced by ARCO Chemical Company. Specific examples of
suitable "Dylark" resins include "Dylark 132", "Dylark 237", "Dylark 238",
"Dylark 250", "Dylark 290", "Dylark 332", "Dylark 350", "Dylark 378",
"Dylark 350 ", "Dylark 378", "Dylark 600", and "Dylark 700".
If either or both of the polymeric components of the polyblends of this
invention are rubber-modified, the resulting blends will still be miscible
with respect to the acid-containing copolymer and the anhydride-containing
copolymer. However, it is to be understood that the rubber or rubbers may
be present as a discrete, finely dispersed phase in a continuous miscible
anhydride-containing copolymer/acid-containing copolymer blend phase. Such
blends are within the scope of this invention and are termed "miscible"
even though phase separation of the rubber modifier may occur. These
blends will typically exhibit one or more as glass transition temperatures
below 0.degree. C. due to the rubber modifier(s) as well as a single
relatively high glass transition temperature due to the miscible acid- and
anhydride-containing copolymer blend components.
To achieve a fully miscible blend, it is critical that the amount of the
.alpha.,.beta.-unsaturated carboxylic acid in the acid-containing
copolymer is not more than 75 percent greater than the amount of
.alpha.,.beta.-unsaturated dicarboxylic acid anhydride in the
anhydride-containing copolymer. For example, if the anhydride-containing
copolymer contains 5 weight percent maleic anhydride, the concentration of
methacrylic acid in the acid-containing copolymer should not exceed 8.75
weight percent (5.times.1.75). Similarly, if 10 weight percent maleic
anhydride is present, the level of methacrylic acid in the other polymeric
component of the blend cannot be more than 17.5 weight percent
(10.times.1.75) to achieve complete miscibility. More preferably, the
concentration of acid is not more than 50 percent higher than the
anhydride concentration.
In the polyblends of this invention, it is also desirable to select an
acid-containing copolymer having the same glass transition temperature as
the anhydride copolymer if the objective is to extend the
anhydride-containing copolymer. In this manner, the heat resistance and
other physical properties of the anhydride-containing copolymer will be
minimally affected. However, this invention may also be used to increase
the heat resistance of an anhydride-containing copolymer by blending it
together with an acid-containing copolymer having a higher glass
transition temperature as the resulting miscible blend will have a Tg
higher than that of the base anhydride-containing copolymer.
The compositions of this invention, may, if desired, be additionally
comprised of one or more additives such as fillers, colorants,
stabilizers, flame retardants, blowing agents, plasticizers, processing
aids (e.g., lubricants), and the like. To improve the stiffness and/or
tensile strength of the blends, a reinforcing filler such as glass flakes
or fibers, carbon or graphite fibers, plastic fibers (e.g., polyamide
fibers), metals, ceramics, silicates, asbestos, titanium dioxide, mica,
talc, or the like may be incorporated. Typically, the amount of
reinforcing filler will be in the range of from about 5 to 40 weight
percent of the total weight of the reinforced blend.
The compositions of this invention may be prepared by any known or
conventional procedure for the blending of thermoplastic polymers. For
example, the blend components may be combined and then melt-processed on a
single- or twin-screw extruder. Processing temperatures of from about
200.degree. C. to 325.degree. C. will generally be suitable. The extruder
blend may be chopped or otherwise formed into pellets or beads for ease in
handling, during packaging, shipping, storage, and use in molding
operation. Solvent blending techniques may also be used to prepare the
subject polyblends.
The compositions of this invention may be shaped into useful molded
articles using any of the known procedures for forming or processing
thermoplastic resins. Suitable methods include, for example, blow molding,
injection molding, thermoforming, extrusion molding, rotational molding,
and the like. The miscible polyblends may also be foamed using methods
suitable for foaming styrene homopolymer or copolymer resins. For example,
pellets or beads of the polyblend may be impregnated with a volatile
blowing agent such as a hydrocarbon, halocarbon, carbon dioxide, air or
the like and then expanded by heating in a closed or partially closed mold
with steam or the like such that the pellets fuse into a foamed molded
article. Extruded foam techniques may also be employed. The polyblends of
the invention may also advantageously be used as components in multilayer
laminates, composites, or co-extruded film products. For example, the
polyblends could be further blended with a polybutylene terephthalate
resin and then laminated with a polystyrene resin.
From the foregoing description, one skilled in the art can readily
ascertain the essential characteristics of this invention, and, without
departing from the spirit and scope thereof, can make various changes and
modifications of the invention to adapt it to various uses, conditions,
and embodiments.
The following examples further illustrate the compositions of this
invention, but are not limitative of the invention in any manner
whatsoever.
EXAMPLE 1
To illustrate the preparation of the miscible polyblends of this invention,
equal parts by weight of a styrene/methacrylic acid copolymer containing
10 weight percent polymerized methacrylic acid (Tg 132.degree. C.) and
"Dylark 332" (a styrene/maleic anhydride copolymer containing about 14
weight percent maleic anhydride and having a Tg of 132.degree. C.,
available from ARCO Chemical Company) were blended by passing the mixture
through a twin-screw extruder at 250.degree. C. The extruded strand was
cut into 1/4" pellets. The blend pellets were then injection molded to
form test specimens. The resulting specimens were clear and exhibited a
single glass transition temperature of 132.degree. C. The miscibility of
the blend components was verified by microscopy and by measurement of
physical properties. The physical properties of the blend were generally
the average of the corresponding physical properties of the individual
components of the blend, as shown in Table I.
TABLE I
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Acid- Anhydride
Containing
Containing
Copolymer
Copolymer Blend
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Tensile Strength, psi
7000 7000 7000
Flex. Mod., psi
500,000 450,000 495,000
DTUL, .degree.F.
224 224 224
Appearance Transparent
Transparent
Transparent
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EXAMPLE 2
Example 1 was repeated using "Dylark 232", a styrene/maleic anhydride
copolymer containing 8 weight percent polymerized maleic anhydride and
having a Tg of 120.degree. C. available from ARCO Chemical Company. As in
Example 1, a fully miscible transparent polyblend was obtained having a
single glass transition temperature of 124.degree. C.
EXAMPLE 3
Example 1 was repeated using a styrene/methacrylic acid copolymer
containing 15 weight percent methacrylic acid and having a Tg of
140.degree. C. As in Example 1, a fully miscible transparent polyblend was
obtained having a single glass transition temperature of 135.degree. C.
COMPARATIVE EXAMPLE 4
To demonstrate the criticality of adjusting the relative proportions of
acid and anhydride in the copolymer components of this invention, Example
3 was repeated using "Dylark 232" as the anhydride-containing copolymer.
The resulting mixture was hazy and exhibited two distinct glass transition
temperatures at 118.degree. C. and 139.degree. C., indicating that the two
polymers were not miscible. In this example, the amount of acid in the
acid-containing copolymer was 87.5% greater than the amount of anhydride
in the anhydride-containing copolymer.
EXAMPLES 5-13
To further demonstrate the use of various acid- and anhydride-containing
copolymers to prepare miscible polyblends in accordance with this
invention, the polymeric components shown in Table II are melt-blended
using the procedure described in Example 1. The following is a description
of the polymeric components of these polyblends.
Acid-Containing Copolymers
A-1: "RYULEX 11", a styrene/methacrylic acid copolymer believed to contain
approximately 11 weight percent methacrylic acid, available from Dainippon
Ink and Chemical Inc.
A-2: "RYULEX 15", a styrene/methacrylic acid copolymer believed to contain
approximately 15 weight percent methacrylic acid, available from Dainippon
Ink and Chemical Inc.
A-3: A styrene/acrylic acid copolymer containing 7 weight percent acrylic
acid, prepared in accordance with U.S. Pat. No. 4,195,169.
A-4: A styrene/methacrylic acid copolymer containing 20 weight percent
methacrylic acid, prepared in accordance with Example 3 of Japanese Kokai
No. 248708/85.
A-5: A styrene/methacrylic acid/methyl methacrylate/acrylonitrile
tetrapolymer containing 65 weight percent styrene, 15 weight percent
methacrylic acid, 10 weight percent methyl methacrylate, and 10 weight
percent acrylonitrile, prepared in accordance with Example 8 of Japanese
Kokai No. 248708/85.
A-6: A rubber-modified styrene/methacrylic acid copolymer containing 82
weight percent styrene, 10 weight percent methacrylic acid, and 8 weight
percent polybutadiene rubber, prepared in accordance with Example 3 of
U.S. Pat. No. 4,631,307.
A-7: A rubber-modified styrene/methacrylie acid copolymer containing 72
weight percent styrene, 13 weight percent methacrylic acid, and 15 weight
percent 57/43 random butadiene/styrene rubber, prepared in accordance with
Example 6 of EP Publication No. 410,607.
Anhydride-Containing Copolymers
B-1: "DYLARK 232", a styrene/maleic anhydride copolymer containing about 8
weight percent maleic anhydride, available from ARCO Chemical Company.
B-2: "DYLARK 290", a styrene/maleic anhydride copolymer containing about 17
weight percent maleic anhydride, available from ARCO Chemical Company.
B-3: "DYLARK 132", a styrene/maleic anhydride copolymer containing about 5
weight percent maleic anhydride, available from ARCO Chemical Company.
B-4: A styrene/maleic anhydride copolymer containing 20 weight percent
maleic anhydride, prepared in accordance with U.S. Pat. No. 2,989,517.
B-5: A styrene/maleic anhydride/methyl methacrylate/acrylonitrile
tetrapolymer containing 65 weight percent styrene, 15 weight percent
maleic anhydride, 10 weight percent methyl methacrylate, and 10 weight
percent acrylonitrile, prepared in accordance with U.S. Pat. No.
4,223,096.
B-6: A rubber-modified styrene/maleic anhydride copolymer containing about
8 weight percent maleic anhydride and about 15 weight percent of a graded
styrene/butadiene block copolymer, prepared in accordance with U.S. Pat.
No. 3,919,354.
B-7: A rubber-modified styrene/maleic anhydride/methyl methacrylate
terpolymer containing 68 weight percent styrene, 15 weight percent maleic
anhydride, and 17 weight percent methyl methacrylate and additionally
containing 14 parts by weight SBR (styrene-butadiene rubber) per 100 parts
terpolymer prepared in accordance with U.S. Pat. No. 4,341,695.
TABLE II
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Example No.
5 6 7 8 9 10 11 12 13
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Acid-Containing Copolymer
A-1
A-2
A-3
A-4
A-5
A-6
A-7
A-1
A-6
Parts by Weight 20 30 40 50 60 70 80 50 45
Ahydride-Containing Copolymer
B-1
B-2
B-3
B-4
B-5
B-6
B-7
B-6
B-1
Parts by Weight 80 70 60 50 40 30 20 50 55
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